It is frequently necessary to be able to move a tool such as a spot welder or grinder about in a limited space, with the ability of positioning the tool to attack a workpiece from virtually any direction. This is particularly the case at a station along an assembly line wherein, for example, motor-vehicle subassemblies are manufactured. Such a system is described in German Pat. No. 2,717,453 filed Apr. 20, 1977 by J. Slootz et al.
In such arrangements there are two principal requirements which typically are traded off against each other. On the one hand the device must be relatively light so as to be easily maneuverable; on the other hand the device must be capable of rigidly retaining the tool or workpiece once it is in position. Thus the user normally has a choice between a light and easy-to-handle system that does not rigidly position the tool or workpiece, and a heavy and cumbersome system that rigidly positions the tool or workpiece. Compromises employ force-amplifying cylinders and the like in heavy-duty systems in an attempt to make a massive arrangement operate as easily as a light arrangement. Such solutions are rarely effective, and in all cases are extremely expensive.